Many color photographic silver halide materials, i.e., color negative films and color prints, today are processed in automated, rapid processing machines popularly known as "mini labs." These processing systems have been developed with the goal of making high-quality prints in the shortest possible time, and typically produce dry prints in 4 minutes or less. The achievement of this goal requires photographic film and papers containing essentially pure silver chloride emulsions and dye-forming couplers that react rapidly and efficiently with the oxidation products of the p-phenylenediamine color developing agents to form the desired image dyes.
In addition to this requirement for high reactivity, the couplers and the dyes derived from them must satisfy requirements for hue and, especially for color papers, stability to light, heat, and humidity, to produce color prints that accurately reproduce the colors of the subjects and do not fade during long-term storage under a wide variety of conditions.
European Patent 571,959 discloses a 1H-pyrazolo[1,5-b][1,2,4]triazole magenta coupler having at the 6-position of the fused ring system a tertiary alkyl group. The presence of this tertiary alkyl group effects a marked improvement in the stability of the image dye to light. However, the disclosed couplers do not have sufficient coupling efficiency for modern rapid processing systems.
U.S. Pat. No. 5,578,437 discloses a 1H-pyrazolo[1,5-b][1,2,4]triazole magenta coupler exemplified by the following structure that is capable of rapid processing and produces an image dye with excellent stability to light. However, the coupling efficiency of this coupler, while improved over some prior art couplers, desirably would be greater for the most rapid processing systems. ##STR3##
It is therefore a problem to be solved to provide a pyrazolotriazole coupler with improved coupling efficiency, which does not sacrifice the necessary image dye properties of excellent hue and, when used in color papers, stability to light, heat, and humidity.